(1) Field of the Invention
The invention relates to a readout scheme for a CMOS Active Pixel Sensor, APS, that reduces 1/f noise and low frequency fixed pattern noise.
(2) Description of the Related Art
U.S. Pat. No. 4,831,451 to Hynecek describes a horizontal scannar having a plurality of stages. The scanner can be used for electronic zooming and panning operations.
U.S. Pat. No. 4,764,814 to Endo et al. describes a solid state imaging device.
U.S. Pat. No. 4,677,490 to Levine describes a CCD imager having a CCD output register having separate means for obtaining low frequency video response and high frequency video response. The low frequency response is obtained by sensing drain current in the output CCD line register. The high frequency response can be obtained from the electrometer output signal after correlated double sampling or after synchronous demodulation at a harmonic of the output CCD line register clocking rate.
U.S. Pat. No. 4,435,730 to Bendell et al. describes the use of output signals from two portions of a CCD imager. The first output signal is derived from a drain diffusion in the form of a signal current. The second output signal is derived from a floating diffusion or floating gate through an on-chip MOSFET amplifier. The first and second output signals are filtered through complimentary low pass filters and high pass filters respectively and then combined to provide a reduced noise output.